The present invention relates to a headlamp for a motor vehicle, which headlamp is provided with an inclination measuring unit for determining whether or not the direction of irradiation of the headlamp, that is, the angle of irradiation of the headlamp in horizontal and vertical planes, is correct. More particularly, the invention relates to an inclination measuring unit for a vehicular headlamp with which the angle of irradiation of the lamp can be corrected with ease.
By way of example, a movable reflector type headlamp will be described in which a reflector is tiltably supported in a lamp body. As shown in FIG. 6, the rear wall of the reflector 202 is supported at three points on the lamp body 201, namely, by two aiming screws 203 and 204 extending in the axial direction of the headlamp and by a swinging fulcrum 205. (Since FIG. 6 is a front view of the reflector, the aiming screws 203 and 204 extend perpendicular to the surface of the drawing.)
More specifically, the aiming screws 203 and 204 are threadably rotatably supported on the rear wall of the lamp body 201. The reflector supporting points of the aiming screws 203 and 204 are arranged so that two straight lines connecting the supporting points and the swinging fulcrum 205 form right angles, for instance. The aiming screws 203 and 204 are turned to swing the reflector 202 about the horizontal axis L.sub.x and the vertical axis L.sub.y, respectively, thereby to adjust the angle of irradiation of the headlamp. In FIG. 6, reference numeral 206 designates a light source, namely, a light bulb mounted in the reflector 202.
On the other hand, a movable unit type headlamp (not shown) is also known in which a lamp-body reflector unit is tiltably supported on a lamp housing. In this case, the reflector is integrally formed on the inner wall of the lamp body. In the movable unit type headlamp, similarly as in the movable reflector type headlamp shown in FIG. 6, the unit is supported on the lamp housing with one swinging fulcrum and two aiming screws. The aiming screws are turned to tilt the unit, thereby to adjust the angle of irradiation of the headlamp.
That is, by turning the two aiming screws, an inclination member (the reflector in the case of the movable reflector type headlamp and the lamp-body reflector in the case of the movable unit type headlamp), which incorporates a light reflecting surface which determines the direction of irradiation of the headlamp, is swung vertically (or about the horizontal axis) and horizontally (or about the vertical axis) with respect to a reference member (the lamp body in the case of the movable reflector type headlamp and the lamp housing in the case of the movable unit type headlamp), thereby to adjust the angle of irradiation of the headlamp.
Recently, a variety of arrangements for measuring the angle of irradiation of a headlamp in the horizontal plane have been proposed in the art, examples of which are disclosed in commonly assigned Japanese Patent Application No. 154630/1988 and Japanese Utility Model Applications Nos. 98397/1988, 121576/1988 and 43979/1989.
However, the measuring devices disclosed in these applications are disadvantageous in the following points: First, a measuring unit for measuring the amount of inclination in the horizontal plane of the inclination member is provided between the inclination member and the reference member, positioned on the upper portion of the headlamp so as to facilitate the reading of the indication. Accordingly, the resultant headlamp is relatively large in height, which militates against the recent tendency to reduce the height of a headlamp as much as possible. Particularly, in the movable reflector type headlamp, with the measuring unit arranged in the lamp body, it is rather inconvenient to read the indication displayed on the measuring unit.
In the aforementioned Japanese Patent Application No. 154630/1988 there is proposed a measuring unit having a scale section protruding rearward of the reference member. However, the measuring unit is still disadvantageous in that it is necessary to form holes in the reference member to mount the measuring unit, which is troublesome. In addition, the adjustment of the measuring unit when coupled to the headlamp is difficult.